For example, in a nuclear power generation plant including a Pressurized Water Reactor (PWR), a light water which is a primary cooling water is used as a nuclear reactor coolant and a neutron moderator to generate high-temperature and high-pressure water which is not boiled over the entire reactor core, the high-temperature and high-pressure water is fed to a steam generator to generate steam by heat exchange, the steam is fed to a turbine generator, and thus, electricity is generated.
In the nuclear power generation plant, in order to secure sufficient stability and reliability of the Pressurized Water Reactor, it is necessary to examine various structures or the like periodically. In addition, when the examination is performed and defects are found, necessary locations related to the defects are repaired. For example, in the Pressurized Water Reactor, the reactor vessel body includes an outlet side tube support for supplying the primary cooling water to the steam generator and an inlet side tube support for adsorbing the primary cooling water which is heat-exchanged by the steam generator. A primary cooling water pipe communicating with the steam generator is connected to the tube support by welding. In addition, since a material of the tube support is different from that of the primary cooling water pipe, a safe end pipe is connected between the tube support and the primary cooling water pipe by welding.
Residual tensile stress generated in a welding portion of the tube support and the periphery thereof may cause stress corrosion cracking. Accordingly, in the related art, there is a water jet peening technology for preventing the stress corrosion cracking by improving the residual tensile stress on the surface into residual compressive stress. In this water jet peening, the residual tensile stress on a surface of a metal member is improved into the residual compressive stress by spraying high-pressure water including cavitation air bubbles on the surface of the metal member in water. For example, as the water jet peening device, there is a water jet peening device disclosed in PTL 1 below.
In the water jet peening device disclosed in PTL 1, in order to keep a distance between a spray nozzle and a surface to be constructed so as to be constant, a guide is attached around the spray nozzle, a slight pressing force is applied to the guide by a pressing device, and the guide comes into contact with the surface to be constructed to trace the shape of the surface to be constructed.